The manufacture of large fabric panels, such as bed sheets, has been a relatively time consuming and expensive operation, involving substantial amounts of manual labor in the forming and sewing of the hems at each end. In this respect, typically, the fabric utilized in the manufacture of bed sheets, for example, will be woven to a predetermined width, and the selvage edges of the woven fabric will form the finished edges of the bed sheet. The web is cut to predetermined length and hemmed to provide the finished product. Typically, the hemming operation involves the forming of both a large and a small hem at each end, so that the raw cut edges are concealed.
While the forming and sewing of fabric hems by automatic means is a well known art, in general, the application of known automatic techniques to the production of large items, such as bed sheets, has remained rather elusive. Because of the very large size of the fabric panels, equipment heretofore proposed for the simultaneous hem folding and sewing of the opposite ends of a bed sheet has proven to be very large and unwieldy, involving not only substantial investment in the equipment, but also occupying an unduly large area of valuable factory space. Moreover, the geometry of such equipment has made it either very difficult or virtually impossible for a single operator to service sewing machines at opposite sides of the machine, so that additional skilled operating personnel may be required in order to maintain an orderly flow of production. In the past, these practical problems have proven sufficiently great that the economics of automatic hem forming and folding on bed sheets and the like has not been very attractive, and the operation has been carried out largely by manual processes.
In accordance with the present invention, a unique and entirely novel approach is taken to the forming and sewing of hems on large panels, such as bed sheets, which enables reliable, consistent, production operations to be carried out with equipment which is highly attractive economically, in comparison to present methods. With the apparatus of the present invention, the two hems are formed and sewed, one more or less directly above the other, regardless of the length of fabric between the hems, and the intervening material is simply gathered in a generally vertical loop. A pair of sewing machines, one positioned above the other, are located laterally adjacent the feeding and folding sections of the fabric. Once the fabric section is cut to length and the hems are folded, the entire unit is held and laterally transferred in a novel and advantageous manner, to be described, and conveyed past the sewing machines for the sewing operations to take place.
In accordance with one of the more specific aspects of the invention, the fabric is fed generally vertically downward into the hem folding section, in a "wrong side out" orientation. The lower hem is folded upside down, and the upper hem, after severing of the section to length, is folded rightside up. The entire fabric section is then controllably transferred laterally through the sewing machines.
In accordance with another specific aspect of the invention, a unique and simplified arrangement is provided for engaging the fabric after initial formation of the hem folds and controllably transferring the fabric laterally, without losing the hem folds. The transfer means both clamps and laterally advances the fabric, and takes the place of the feed dogs of the sewing machines, which are rendered inoperative. In addition, the transfer means are sufficiently responsive to enable high speed sewing and back tacking, as is appropriate in a commercial production sewing operation.
In accordance with a further specific aspect of the invention, a novel arrangement of fabric supporting and guiding plates is provided which accommodates a generally vertically downward, gravity movement of the fabric into precisely measured limit positions to accommodate the necessary cutting and hem folding operations. Thereafter, selected ones of the guide plates are movable into new positions more appropriate for supporting of the fabric during the lateral transfer and sewing operations .